multimedia & communication lab. t.120 : data protocol for multimedia conferencing advanced...
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Multimedia & Communication
Lab.
T.120 : Data Protocol for Multimedia Conferencing
Advanced multimedia
4/27/1999
Jeong, Hwanseok
Multimedia & Communication
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Contents
Overview Normative references Introduction to Multimedia Communication The T.120 System Model T.120 Infrastructure Recommendation Application Protocol Recommendation T.120 Compliance References
Multimedia & Communication
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Normative reference
ITU-T Recommendation T.121(1996), Generic Application Template ITU-T Recommendation T.122(1993), Multipoint Communication Service
for Audiographic and Audiovisual Conferencing service definition ITU-T Recommendation T.123(1993), Protocol Stack for Audiographics a
nd Audiovisual Teleconference Application ITU-T Recommendation T.124(1995), Generic Conference Control ITU-T Recommendation T.125(1994), Multipoint Communication Service
Protocol ITU-T Recommendation T.126(1995), Multipoint Still Image and Annotat
ion Protocol ITU-T Recommendation T.127(1995), Multipoint Binary File Transfer Pr
otocol
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Overview
T.120 recommendation series : multipoint communication service for use in multimedia conferencing environments
T.120 Introduction for the T.120 series, showing the inter-relationships
between the constituent recommendation requirements for compliance to T.120 for conferencing
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Introduction to Multipoint Multimedia Communication
Multipoint communication : interconnection of multiple terminals MCU(Multiple Control Unit), or more simply a bridge, is required T.120 series : the components providing both a data communications se
rvice, and a management service for any other media services present MCU
nodes without terminal functionality, acting as bridging nodes, bridging data and other media streams present in the connections
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Introduction to Multipoint Multimedia Communication(cont’d)
Terminal Terminal
TerminalMultiportterminal
Multiportterminal Terminal
Point to point (The simplest case of a multipoint connection)
Chain Connection with terminals acting as data bridges
< Examples of Multipoint conference configurations showing various connection topologies and Node types >
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Introduction to Multipoint Multimedia Communication(cont’d)
< Multipoint topology-3 MCUs providing connection to allow multipleterminal to participate in a conference >
MCU
MCU MCU
Terminal Terminal Terminal Terminal
Terminal
Terminal
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Introduction to Multipoint Multimedia Communication(cont’d)
MCU MCU
Terminal Terminal
Terminal
TerminalTerminal
TerminalTerminal
Terminal
LAN Gateway-Router-
Terminal Terminal Terminal
LAN Gateway-Router-
Corporate Network A
Corporate Network B
PSTN
ISDN
PSTN
PSTN
ISDNISDN
ISDN
Public Network
< < Example of a mixed-network conference topology >
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T.120 System Model
…
User Application(s)(Using Both Standard and Non-standard Application Protocols
User Application(s)(Using Non-std. Protocol)
T.127 (MBFT)T.126(MSIA)
Application Protocol Entity
Generic Conference Control(GCC) T.124
Multipoint Communications Service(MCS) T.122/125
Network Specific Transport Protocols T.123
Node Controller
ITU-T T.120 ApplicationProtocol Recommendation
User Application(s)(Using Std. App. Protocol)
…Non-Std. App.Protocol Entity
ITU-T T.120 Infrastructure Recommendatios
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T.120 System Model(cont’d)
Comprised of a communications infrastructure and the application protocols
User Application use the services offered by the T.120 series will generally be multipoint aware and designed to use the T.120 s
ervices by GCC and MCS T.121(Generic Application Template) provide on how to utilize th
e T.120 infrastructure in a consistent way
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T.120 System Model(cont’d)
Application Protocols Protocol Data Units(PDUs) + actions for App. peer-to-peer commun
ication The T.120 series includes application protocols designed to support
multipoint conferencing Application Protocol Entity
an instance of an Application Protocol ARM(Application Resource Manager) + ASE(Application Servi
ce Element) ARM : generic functionality relevant to all protocols ASE : application specific functionality Both of these are described in T.121(Generic App. Template)
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T.120 System Model(cont’d) Node Controller
T.120 management role at a terminal or MCU issue primitives to the GCC provider which starts and control the commun
ication session : outside the scope of the T.120
Communication Infrastructure multipoint connectivity with reliable data delivery Three components : GCC, MCS, Transport Protocol Profile
Networks ISDN : Integrated Services Digital Nerwork CSDN : switched or permanent digital circuits PSDN : Packet Switched Data Network using X.25 PSTN : Public Switched Telephone Network B-ISDN, LAN under study
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T.120 Infrastructure Recommendation
Protocol Stacks for Audiographic and Audiovisual conferencing - T.123
Multipoint Communication Service(MCS) - T.122, T.125 Generic Conference Control (GCC) - T.124
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T.123 : Protocol Stacks for Audiographic and Audiovisual conferencing
Network specific transport stacks for each supported network
MCS takes the transport pairs from the layer below it and maps them into a multipoint domain
T.125 - Multipoint Communications Service(MCS)
ISDNTransport
NetworkIndependent
Layer
NetworkDependent
Layer
CSDNTransport
PSDNTransport
PSTNTransport
B-ISDNTransport
NLANTransport
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T.122, T.125 : Multipoint Communication Service(MCS) T.122 : defines the MCS service T.125 : specifies the data transmission protocol MCS : multipoint “engine” of the T.120 conference takes point-to-point transport connections provided by the la
yer below it and combine to form a multipoint domain MCS Provider(Top Provider) acting as the resource server f
or the domain MCS app direct data within domain via the use of channel token are the last major facility provided by MCS
services are provided to grab, pass, inhibit, query token
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T.124: Generic Conference Control(GCC)
Comprehensive set of facilities for establishing and managing the multipoint conference
to maintain information about the nodes and applications that are in a conference
Applications create conferences, join conferences, and invite others to conference
conference security capabilities for supporting the concepts of conductorship i
n a conference
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Application Protocol Recommendation
The Generic Application Template(GAT) - T.121 Multipoint Still Image and Annotation Protocol(MSIA) - T.
126 Multipoint Binary File Transfer(MBFT) - T.127 Non-Standard Application Protocols
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T.121 : The Generic Application Template(GAT) A conceptual model of a T.120 application protocol A guide to application protocol developers and user
application developers on how to utilize the T.120 infrastructure to best effect
Two distinct parts ARM(Application Resource Manager) + ASE(Application Service
Element) ARM : generic functionality relevant to all protocols ASE : application-protocol-specific functionality Both of these are described in T.121(Generic App. Template)
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T.126 : Multipoint Still Image and Annotation Protocol(MSIA) To be used by a broad set of user application that require
inter-operable graphical information exchange in a multi-vendor environment
white boarding, annotated image exchange, hard copy image exchange, remote computer application piloting, screen sharing
manage the conference-wide synchronization of multi-plane/multi-view graphical workspaces
Advanced option keyboard and pointing device signaling
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T.127 : Multipoint Binary File Transfer(MBFT) to support interchange of binary files within an interactive
conferencing or group working environment no restriction on the content of the files to be transferred versatile flexible Optional advanced feature
Broadcast of multiple files simultaneously Private distribution of files to a selected subset of the conference Conductor control of file distribution
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T.127 : Multipoint Binary File Transfer(MBFT)
MBFT MBFT MBFT
MCSProvider
MCSProvider
MCSProvider
Top MCSProvider
Node that require file A
Node that requirefiles A and B
Control channel
Data channel
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Non-Standard Application Protocols
Must use GCC in a way that does not risk conflict with other app. protocol entity
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T.120 Compliance
transport Protocol stack profile(T.123) multipoint Communication Service protocol(T.125) mandatory parts of Generic Conference Control(T.124) mandatory parts of any standardized app. Protocol
T.121
T.123
T.124
T.125
T.126
T.127
conditional
mandatory
mandatory
mandatory
conditional
conditional
Depend on condition
Depend on condition
Depend on condition
Depend on condition
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References
ITU-T Recommendation T.120(1996), Data Protocol for Multimedia Conference.
“A Primer on the T.120 Series Standard”, http://www.databeam.com/ccts/